Breathing Easy on the Space Station

At present,
carbon dioxide is removed from the air by a machine on the Zvezda
Service Module based on a material called "zeolite," which acts
as a molecular sieve, according to Jim Knox, a carbon dioxide
control specialist at MSFC.

The removed CO2 will be vented to space. Engineers are also thinking
of ways to recycle the gas.

In addition to exhaled CO2, people also emit small amounts of other
gases. Methane and carbon dioxide are produced in the intestines,
and ammonia is created by the breakdown of urea in sweat. People
also emit acetone, methyl alcohol and carbon monoxide -- which
are byproducts of metabolism -- in their urine and their breath.

Activated charcoal filters are the primary method for removing these chemicals
from the air.

This diagram shows the flow of recyclable resources
in the Space Station's Environmental Control and Life Support
System (ECLSS).

Maintaining
a healthy atmosphere is made even more complex by the dozens of
chemicals that will be used in the science experiments on board
the ISS.